Picture reproducer



April 18, 1939. R. BARTHELEMY PICTURE REPRODUCER Filed NOV. 8, 1934 '0 KBox'i'helem IN VE NTOQ.

Pun ATTY.

Patented Apr. 18, 1939 UNITED STATES PATENT OFFICE PICTURE REPRODUCERMontrouge, France Application November 8, 1934, Serial No. 752,046 InFrance November 14, 1933 3 Claims.

In most devices for the reconstruction of images by means of a cathoderay oscillograph, the cathode beam is oscillated by means of two sets ofplates perpendicular to one another. The beam describes juxtaposedparallel lines to reproduce the image on the screen at one end of theoscillograph.

According to the present invention, the cathode beam is moved to and frobehind a slit which it illuminates. The successive lines are juxtaposedto constitute the image, a moving optical system being in the path ofthe light issuing from the slit.

A synchronous motor produces the releasing impulses of the oscillographwhich control the forward and backward movement of the beam at thefrequency of the lines. The motor moves also the optical system, usuallya drum carrying Wide mirrors, which casts the image in the directionperpendicular to the lines of analysis at a speed, say of 16 to 24images per second.

This arrangement permits the diminishing of the effect of the modulationon the size of the light spot. In effect, as this luminous spot movesalong a straight line, an obturator can be placed before the groundglass fluorescent screen of the oscillograph. The obturator is providedwith a rectilinear slit of a suitable width which allows the appearanceonly of that part of the spot which corresponds to the width of a singleanalysis line. The apparatus is so adjusted that the strongestmodulation gives a white corresponding to the maximum concentration ofthe cathode beam and in this manner the display which corresponds to thedark parts is not substantially restrained and good definition of theimage is obtained whatever the amplitudes of the modulation may be.

The oscillograph can be of the usual type, not specially adapted for usewith television systems, and the modulation can be applied to thefocusing anode. Moreover, the apparatus need only have two deflectingplates instead of four.

The present arrangement permits the dimensions of the image to beincreased; one can, in effect, utilize the complete diameter of thefluorescent screen for the length of the image, whereas in priorstructures only two-thirds of the diameter could be used.

Other improvements permitting the light issuing from the slit to bemodulated while maintaining constant the intensity of the cathode beamwill be described in detail hereinafter.

The invention will be best understood with the aid of the followingdescription and the annexed drawing in which Figs. 1 to 3 exemplifythree diagrammatic embodiments of the device.

A cathode ray oscillograph T (Fig. 1) is provided with a cathode K, afocusing cylinder W, one or more accelerating anodes A, two deflectingplates P1 and P2, and a fluorescent screen E. In front of this screen isplaced an opaque diaphragm D provided with a slit F1, F2 perpendicularto the plates P1 and P2. The width of this slit is a function of thewidth of the lines of analysis of the image and is such that thesuccessive lines reproduced are juxtaposed. The apparatus is adjusted insuch a manner that the point of impact of the cathode beam on the screenE moves behind the slit F1, F2.

The fluorescent screen can be limited to the useful part which isdisclosed by the slit F1, F2. Moreover the screen diaphragm assembly canhave an elongated form in the direction of the slit, for example, it maybe elliptical or in the form of a very flat rectangle. This arrangementis particularly useful for the obtaining of large images. In front ofthe screen E is a rotating mirror drum M, the mirrors being parallel tothe axis of rotation and being symmetrical with respect to this axis.The axis of rotation is itself parallel to the slit F1, F2. Each mirrorwill produce a synthesis of the image, by juxtaposing the successivelines for an observer placed, for example, at O, and to the observer thereflected rays seem to emanate from a real image behind the oper-; atingmirror.

On the axis of this drum, or on a shaft connected thereto by a train ofgearing B (Fig. 2), is mounted the. rotor' of a synchronous motor S.This latter is fed for example by the alternating current mains anddrives a phonic wheel generator R. The point voltages of this generatorrelease a device C such as a Thyratron which controls the movement ofthe cathode beam, by the action of plates P1, P2.

The mirror drum may be replaced by a lens disc projecting the image ofthe cathode spot on to ground glass screen Without departing from thescope of the present invention (see Fig. 3).

In order to obtain a projection on to a screen of ground glass, one ofthe most practical processes consists in constituting a beam with afixed lens L (Figure 2) of large aperture, placed at a suitable distancefrom the fluorescent spot and in directing this beam on to a turningdrum provided with mirrors; this method avoiding the grave deformationswhich arise with the devices described above and not requiring mirrorsof large dimensions.

If it be so arranged that the entire image must be screened by one ofthe mirrors of the drum, the latter must turn at a relatively low speedwhich gives rise to difficulties in the synchronous motor as well as inthe dimensioning of the toothed wheel for releasing the device 0. On theother hand, difiiculties can equally be encountered in the use ofreduction gears on ac count of the required precision.

One improvement consists in mounting the mirror drum directly on themotor shaft which turns, for example, at a speed of twenty fiverevolutions per second, in placing the observer of the screen at such adistance from this drum and in turning the mirrors in such a manner thateach provides a fraction of the height of the image. The total imagewill be obtained after one complete revolution. Under these conditions,the mirrors will not be all perpendicular to the radius of the drum butwill remain parallel with its axis.

In the device which has just been described the variations of intensityof the luminous flux leaving the slit F1, F2 are obtained by modulatingthe cathode beam by the application of the modulation voltage betweenthe cathode K and one of the anodes.

Another improvement of this device consists in maintaining the intensityof the cathode beam constant and in displacing the said beam in adirection perpendicular to the slit F1, F2 in such a manner that inorder to obtain clear surfaces, the spot of impact of the cathode beamon the screen E is seen in its entirety through the slit F1, F2 and sothat, for the darkest surfaces, the spot disappears partially or whollybehind the opaque part of the diaphragm. A slight displacement of thespot, of the order of a millimeter, is obtained by the application ofthe modulating voltage to a pair of deflecting plates P1 and P2 (Figure2) perpendicular to the plates P1 and P2 which control the sweeping; andadjustable continuous voltage is connected in series with the modulatingvoltage which, in general, can be less than one volt. This continuousvoltage enables the mean position of the spot on the slit to be adjustedin the absence of modulation. Its variation will enable the value of theblack parts to be increased, contrasts to be accentuated and, if needbe, the whole image to be reversed if, for example, the mean position ofthe spot is fixed towards the top of the slit in place of arranging ittowards the bottom thereof.

With this device there is no risk of the displays of the spot being afunction of the modulation since the intensity and speed of theelectronic beam remain constant. This will permit the use of thisintensity at the maximum and will permit the obtaining of a very largequantity of light from the tube.

The method which has just been described gives a powerful modulationwhich is rather difficult to regulate, because the amplitude of thedisplacement of the spot must be very exactly adjusted.

Another improvement produces a variable light behind the rectilinearslit of the oscillograph because the luminous impression on the eyevaries inversely to the rapidity of displacement of the spot.

The principle of this consists in applying to the pair of deflectingplates P1 and P2 producing the vertical deviation of the spot, a highfrequency voltage modulated by the image current.

Calculation and experiment show that the speed of passage of theluminous spot in front of the slit is proportional to the amplitude ofthe modulation at each instant, subject, of course,

"to" the use of an auxiliary frequency which is clearly greater than thehighest frequencies contained in this modulation.

The spot is then moved under the influence of two components:

(1) 'A component of constant speed which moves it in the direction ofthe slit and which provides the exploration of a line of the image;

(2) A component, perpendicular to the slit, of high frequency and of anamplitude which is variable as a function of the modulation voltage, thedirection of application of this component being so chosen that theclear parts of the image correspond to the smallest amplitudes'of theauxiliary oscillation.

Thus I obtain great speed of displacement of the beam perpendicularly tothe slit when the dark parts are transmitted and the beam' is onlyslightly displaced and at a slow'speed when the clear parts appear.

The slit then appears to be variably illumi nated and all the feeblevariations of illumination are faithfully transmitted. In order toutilize the maximum possible amount of light, I provide a minimumamplitude for the oscillation of the beam equal to the width of the slitand place the slit in the mean position of the beam.

In order to increase the definition in the horizontal direction, thebeam can be concentrated to a maximum so that a much better definitionof the limit frequency can be'obtained than with a diameter of themoving luminous point which is at least equal to the width of theline'of analysis. 7 V

The local oscillation modulated by the image current need not be above adozen. volts and can be reduced to one volt under the influence of theclear parts. An oscillator valve of small power is thus suflicient.

One can even do without such a lamp by providing in the transmission anauxiliary carrier wave of a frequency of some hundreds of kilocycles,modulated by the image current and by applying this carrier wave,without detection, and through the intermediary of an ordinary amplifierto the deflecting plates P1 and P2 of the tube.

What I claim is:

1. In an apparatus for the reconstitution of images, the combinationwith a cathode ray 'oscillograph comprising two deflecting platesimparting a backward and forward movement to the cathode beam, aluminous screen, in the path of the cathode beam, and an opaquediaphragm adjacent said screen and having a slit swept by the cathodebeam, of a rotatable disc arranged outside of said oscillograph, meansto rotate said disc at a predetermined speed, and a series: of lensesmounted on. said disc along a circle concentric with the axis ofrotation of said disc to be placed successively in the path of the lightrays emanating from said slit and to deflect said rays at successivelyvarying angles so as to juxtapose the successive luminous images of saidslit along parallel lines when said disc is rotated.

2. A device as claimed in claim 1, wherein said means to drive therotatable disc includes a synchronous motor, said device comprisingfurther a generator of periodic current for feeding a predeterminedamplitude to said deflecting plates, said generator being driven by saidsynchronous motor.

3. In an apparatus for the reconstruction of images, the combinationwith a cathode ray oscillograph comprising two deflecting platesimparting a backward and forward movement to the cathode beam, aluminous screen in the path of the cathode beam, an opaque diaphragmadjacent said screen and having a slit swept by the cathode beam, andtwo auxiliary deflecting plates perpendicular to said first mentioneddefiecting plates to imp-art to the cathode beam, a displacementperpendicular to said slit, of a rotatable disc arranged outside of saidoscillograph, a series of lenses mounted on said disc along a circleconcentric with the axis of rotation of said disc to be placedsuccessively in the path of the light emanating from said slit and todeflect said rays at successively varying angles so as to juxtapose thesuccessive luminous images of said slit along parallel lines when saiddisc is rotated, a fixed optical system positioned between said lenseson said disc and said slit at a suitable distance from the latter toconverge the light emanating from said slit, a discharge tube forfeeding periodic currents of a predetermined amplitude to said firstdeflecting plates, a phonic wheel controlling said discharge tube, asynchronous motor to drive said rotatable disc and said phonic wheel,and means to feed to said auxiliary plates an amplitude in accordancewith the modulations of the image current.

RENE BARTHELEMY.

